1. Field of the Invention
The present invention relates to a camera capable of superimposition display in a finder.
2. Description of the Related Art
Hitherto, there has been known the so-called superimposition display technique utilized in a camera having a plurality of distance measurement fields of view or the like. In the so-called superimposition display, the selected distance measurement field is superimposed onto the subject image in the finder field of view and displayed. In particular, the superimposition display technique employing light emission has the following advantages:
(1) The display will almost always be recognized by the photographer because the display device is lit to draw the photographer's attention;
(2) The display will almost always be recognized by the photographer even when the subject is not bright; and
(3) A larger variety of colors can be used for the display color.
Such a camera having a superimposition display device is disclosed for example in Japanese Patent Laid-Open Nos. 61-249034 and 6-130481, both of which have not been filed abroad.
Japanese Patent Laid-Open No. 61-249034 discloses a single-lens reflex camera utilizing a superimposition display device of the light-emission type. In the camera, the display device illuminated from behind is placed below the mirror box, and the light from the subject is projected onto a focusing screen via a half transparent mirror that splits the light beam into a beam section which is directed to the finder system and a beam section that is directed to the focus detecting device.
Japanese Patent Laid-Open No. 6-130481 also discloses a camera utilizing a superimposition display device of the light-emitting type. In the camera, a display device in which the grooves of the diffraction grating is filled with liquid crystal is placed adjacent to the focusing screen. The diffraction light is turned on and off based on changes in the diffraction factor of the liquid crystal that occur when an electrical field is applied, so as to obliquely illuminate the display device to achieve light-emission type superimposition display.
In the superimposition display technique disclosed in Japanese Patent Laid-Open No. 61-249034, however, the image on the liquid crystal display device is magnified a few times when it is projected onto the focusing screen, thus preventing the image to be projected onto the proper location on the focusing screen. Consequently, a displacement from the actual distance measurement field occurs frequently.
In the superimposition display technique disclosed in Japanese Patent Laid-Open No. 130481, such a problem occurs less frequently because the camera comprises a display device that can actually be seen through the finder, and an illuminating device that illuminates the display device. In recent years, however, a camera having a large number of distance measurement fields of view has been more widely used. When this display technique is used in such a camera, other problems arise.
In other words, when display sections serving as focus area frames are provided in correspondence with the positions of the measurement distance field of view of the distance-measuring device, each of which frames together occupy a rather larger area of the photographic screen, the illuminating device must selectively illuminate over a large area of the screen to illuminate the display device. Since the illuminating device illuminates display elements from an oblique angle, the display devices that can be actually illuminated are limited, for example, to those along the horizontal central line of the photographic screen, so that display elements can only be disposed along the horizontal central line. An attempt to solve such a problem causes the size of the camera to increase because a large space is required for the illuminating device.